Ignition light stayed on after key withdrawn once only!

[Pete.C]

Hi Guy's this is my first post so I hope I am in the right place? I have an E46 330 petrol saloon, 2000 model and I am in the UK. I use the car daily and if the weather is cold I always make sure it gets a good run out for 20-30 minutes to keep the battery topped up.

The other week i had a flat battery and the AA guy, (Roadside Assistance) checked over the vehicle and said the battery is fine, only 11 months old, so there must be a drain on it somewhere and that was the extent of his capability and responsibility. The next day I took it a vehicle electrician I know and left it with him as he was very busy. A week later he got round to looking at it and it started fine so he said there wasn't anything he could do if there was no obvious fault or fault code, and because he was very busy I collected it and drove it home without any issue.

The following day took it out for a good 30 minute drive and it performed fine but this morning I put the ignition key and it wouldn't start so I assumed the battery was flat. However I took out the key and the ignition lights stayed on so i rang the electrician and he suggested hooking it up to my son's car and jump starting it, and it started fine but I got the 'check engine' symbol. As he is quite busy at the moment he suggested taking it out again for another 30 minute run, try it again in the morning and report back. It started fine and drove as it usually does without any problems but still had the 'check engine' symbol.

I have taken the car out for shopping and getting fuel etc so it has been started at least 5 or 6 times but there has been no repeat of the ignition lights staying on after the key is removed so there has only been 1 instance of that issue.

He suggested I may have left something on, but why was it ok at his place after a week of not being used? I took some video using my iPhone in my glove box and boot to make sure the lights went out, which they did. He also suggested it could be the ignition switch or even the E.C.U, but other that than it would potentially be a long process of elimination!

A friend of mine has a cheap OBD fault reader and he hooked it up and got the following code and message "P0604 Internal Control Module Random Access Memory (RAM) error. So tomorrow I will ring the electrician and see what he thinks but as he is really busy it may be a few weeks before he can look at it so I was wondering if anyone could give some advice?

[Muzz258]

Did a Google search on the P0604 code. It seems to be uncommon.

Possible causes are:
- Came as a result of a flat battery or trying to start the car due to a partly flat battery
- The RAM in the engine computer (DME) is faulty and you need a new DME.
- There is a blown fuse causing a low voltage problem with the DME. Check all fuses and the 5 special ones in the box by the DME.

[Pete.C]

Thanks Muzz. I am no mechanic but i will check the fuses and let you know. Is there a way to test if the RAM in the DME is faulty? and if it is defective is it an expensive job to get fixed? I started the car this morning without any problems and drove it for around an hour without the engine check light coming on. The car has only done around 85000 miles and runs sweet as a nut so I really don't want to get rid of it. Another chap told me to buy a battery power pack and keep it in the car in-case of a flat battery so I at least have a way to help myself, which I now have. He also suggested locking the car with the key in the door instead of activating the alarm as the alarm itself could be causing the issue?